It will be appreciated that previous distance sensors have been manufactured in many versions or configurations and have been based on different operating principles. For example, one known type of sensing device is shown and described in German published Patent Application DE-OS No. 16 73 938. In this previously known sensing device, there is provided a rectangular iron yoke having two air gaps. In the one air gap, there is situated an element sensitive to a magnetic field. A regulating member is inserted in the other air gap. Depending on how far the regulating member is inserted into the other air gap, the magnetic flux emanating from the permanent magnet and passing through the yoke is varied. The variation in flux is recognized by the sensing element and the magnetic field is transformed into an electrical voltage which is a function of the distance that the member is inserted into the air gap.
One disadvantage of this previous arrangement is that it takes up a relatively large amount of space. In addition, only short distances can be sensed and measured.